code: def num_classes(self):
      return self._num_classes
  
imports: import numpy
  import os
  import json
  import h5py
  from tqdm import tqdm
  from torchmeta.utils.data import Dataset, ClassDataset, CombinationMetaDataset
  from torchmeta.datasets.utils import get_asset
label_desc: Use image node_id 3 for calling the BachClassDataset obj's underlying member method code with example usage: obj.num_classes() and returns: self